1. Field of the Invention
This invention relates to a hot-melt-adhesive composite fiber capable of being adhered by heating. More particularly it relates to a hot-melt-adhesive composite fiber which has a broad temperature range of hot-melt adhesion; exhibits a low heat-shrinkage over the whole temperature range thereof; has a high tenacity; and is suitable to production of a non-woven fabric having superior restoring properties, bulkiness, draping properties and feeling.
2. Description of the Related Art
A process for producing a non-woven fabric by utilizing the heat melt adhesion of a lower melting point component of a composite fiber consisting of a plurality of polymers having different melting points has been well known and the process is suitable mainly to production of a non-woven fabric having a medium or low basic weight. Japanese patent publication No. 55-17807/1980 discloses a polyolefin composite fiber consisting of a fiber-forming component of polypropylene and an adhesive component of polyethylene. However, since such a fiber has a relatively small difference in the melting points of both the components, the temperature range in which heat-melt adhesion can be carried out at a state of low percentage heat shrinkage is so narrow that correct temperature control is required in the production of non-woven fabrics. Japanese patent application laid-open No. 57-176217/1982 discloses a composite fiber consisting of a fiber-forming component of a polyester and an adhesive component of polyethylene or polypropylene. Since this fiber has a large difference in the melting points of both components, there is an advantage that the heat-melt adhesion temperature range is far broader than that of the above polyolefin composite fiber, but on the other hand, since the compatibility of the polyester with the polyolefin is inferior, there is a drawback that both the components are liable to separate from each other. Further, according to Japanese patent application laid-open No. 57-176217/1982, composite fibers are subjected to heat treatment in advance, in order to prevent shrinkage at the time of hot-melt adhesion, thus both the components of the resulting composite fibers are more liable to peel off from each other so that there are drawbacks that non-woven fabrics using such composite fibers have a weak nerve; are inferior in the restoring properties after repeated load applications; and are so weak in abraision resistance that the peeled polyethylene component is separated and forms a powder.